Acid-base disorders were investigated in 50 calves with chronic indigestion and metabolic acidosis. In the calves that were unable to stand up, the acidosis was significantly more severe than in the calves that could stand up. The anion gap and four different components of the base excess were calculated by the method described by Fencl. The anion gap was high in more than half of the calves, and it was significantly associated with the base excess due to unidentified anions. However, in seven of the calves, the excess of unidentified anions would not have been detected without the calculations, which made it possible to measure the effect of sodium, chloride, plasma protein and unidentified anions on the acid-base balance. Twenty-four of the calves had a combination of hyperchloraemic and high anion gap metabolic acidosis. Changes in sodium and plasma protein concentrations had a minor impact on the calves' acid-base status.